Study on the modification of fly ash as a coagulant

Abstract

This study was carried out to produce a complex coagulant containing aluminum and iron salt from coal fly ash by H₂SO₄ acid. An application of this extracted solution as a coagulant was also investigated by the jar-test process. Fly ash collected at the Electrostatic precipitation (ESP) system in Mong Duong thermal power plant are mainly round and fine particles with diameters ranging from 0.2-8 µm, containing aluminum and iron of 15 and 6% respectively. At a room temperature of 25^oC, with 1 M H₂SO₄ acid solution and the retention time of 20 minutes, the maximum contents of around 60.16 mg.l^-1 of Fe and 4.37 mg.l^-1 of Al were the most favorable to convert aluminum and iron from mineral forms to sulfate salt-based forms. The produced complex coagulants from fly ash of the Mong Duong power plant are proved to be effective for total suspended solids (TSS) removal from wastewater where the highest efficiency achieved 83.6% at the coagulant solution ratio of 5% (w/w) with a concentration of TSS in the initial wastewater was 60 g.l^-1. The positive results from this study open a meaningful approach toward a huge of fly ash produced from thermal power plants as well as other coal-burn-related activities in Vietnam.